Work supporting mechanism for grinding machines



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WORK SUPPORTING MECHANISM FOR GRINDING MACHINES Filed Nov. 7, 1928 2 Sheets-Shea?I 2 HERBERT AS1 EVEN ALBERT G. BELDEN A @am E Patented Dec. 22, 1931 UNITED STATES HERBERT A. SILVEN AND ALBERT G. BELDEN, OF WORCESTER, MASSACHUSETTS,

PATENT OFFICE ASSIGNORS TO NORTON COMPANY, OE WORCESTER, MASSACHUSETTS, A CORPORA- TION OF MASSACHUSETTS WORK SUPPORTING MECHANISM FOR GRINDING- MACHINES Application led November This invention relates to grinding machines and more particularly to a work holding and clamping mechanism capable of use in machine tools, such as a double-head grinding machine for crankshaft grinding and the like.

Heretofore various mechanisms have been employed for clamping a crankshaft in a double-head machine so that the drive between the two heads might be equalized to avoid any undue torsional strains of the shaft during the grinding operation. These mechanisms have comprised manually operable clamping devices so constructed as to necessitate the operation of swinging a clamping member into place and then turning a clamping bolt or nut by means of a suitable wrench. to lock the shaft in position on the work head. Likewise, after the grindingl operation the operator had to slack-off on the clamping bolt or nut and swing the clamping member out of place before he could lift the shaft out of the machine and replace it with a shaft. This required considerable f time on the part of the operator and reduced the productive output of the machine.

It is the principal object of this invention to eliminate this diiiicultv and to provide a clamping mechanism which is mechanically operated with a minimum amount of attention on the part of the operator, thereby increasing the production per machine.

It is a further object to provide a suitable mechanism for clamping the work piece in f place by a yieldable mechanism arranged to exert a definite pressure upon the work piece so as to insure the work being securely clamped in place for the grinding operation, and particularly to provide a mechanism which tends to clamp the work piece automatically but which may be released mechanically at the will of the operator.

In previous mechanisms there has been no cooperation between the clamping mechanism and the control for the work rotation. With 7, 1928. Serial No. 317,820.

the ordinary type of clamping mechanism, such as has heretofore been used in-crankshaft grinding, the operator had to first clamp the shaft in place and then as a second operation start the work rotation before the grinding wheel could be brought into contact with the work. If, for any reason, the operator did not securely clamp the crankshaft in place before starting the work rotation, the loosely clamped shaft might cause injury to the grinding Wheel and machine as Well as the products being ground, and also endanger the life of the operator. Also, if the work support were located in an inverted position when the clamping jaw was released, the work would fall from its support; hence it is desirable, in a machine which has a mechanically operated clamping device, to so construct the mechanism that the work cannot be released except when properly supported.

It is a further object of this invention to overcome this difficulty and to provide an interlocked arrangement of the control for' the work clamping mechanism and the clutch which controls the starting and stopping of the work rotation.

It furthermore is an object to provide a mechanism which cannot be operated to release the work from its support when it is so positioned that it would fall from the clamping support.

As shown in the drawings, one embodiment showing the operating valve together with the connections lo the cylinder mechanism on the work heads;

Fig. 5 is a fragmentary detail View showing a safety device which prevents unlocking the clamping device when the work holders are in an inverted position;

Fig. 6 is a fragmentary detail View taken approximately on line 6 6 of Fig. 4 showing the connections between the control lever and the valve stem;

Fig. 7 is a detail longitudinal sectional view taken approximately on the line 7 7 of Fig. 1, showing the thrust bearing connections between the clamp operating member and the actuating mechanism; and

Fig. S is a View similar to Fig. @t on a reduced scale showing the double acting piston arranged for actuating the Work clamping members.

This invention provides an automatic clamping mechanism for a grinding machine, such as crankshaft grinding machines and the like and which is particularly useful in a double-head' grinding machine in which the head and foot stocks are each provided with a clamping mechanism to support and rotate the work during the grinding operation. In the form illustrated, a clamping device for holding the work during rotation may comprise a rotatable holding member and a clamping jaw which is n'iovi-fd into engagement with the periphery of an end of the work by a power mechanism controlled by the operator. The clamping jaw may be moved by a spring actuated mechanism into engagement with the work, and it may be released by a fluid pressure device. The Work is positively rotated by a clutch controlled mechanism and in order that the clamping jaw may not be released until the work rotation has been stopped, and vice versa, the control mechanisms for the clutch and the clamping jaw are so interlocked or arranged that. they must be operated in a deinite sequence. Also, the jaw cannot be released, because of a locking device, unless the holding member is in such a position as to support the Work When the jaw is out of contact therewith.

The double-head crankshaft grinding machine illustrated in the drawings comprises a work supporting table 11 Which is adapted to slide on suitable ways on the machine base not shown) and adapted to support the Work blank in operative relation With a grinding Wheel 12 which may be mounted on any of the old and well-known types of Wheel slide. The wheel slide is provided with any suitable feed (not shown) mechanism so that the grinding Wheel may be fed into the Work to grind the same to the desired size. The work table 11 is provided with a pair of Work supporting heads 14C and 15 which as illustrated u may he made integral with the table 11 or if preferred may be bolted rigidly to the table and provided with a suitable adjustment so that the heads may be moved laterally oll the table to align the axis of one head with the axis of the other.

The heads let and 15 are provided with work supporting spindles 16 and 1T jour nalled in the partial bearings 18 and provided with floating bearing members 19 which may be adjusted relative to the lixed portion of the bearings by screws 2l). For turther details of this bearing construction together with the drive for the spindles, rcterence may be had to the United States patent to Norton Xo. 1,563,231() oi November il. 15H5.

The work supporting spindles 16 and 1T are provided at their outer ends with sprockets and 2li respectively which are in turn connected with sprockets 2T and 25 by link driving chains 2i) and 30. '.l'he sprockets il? and 2e are mounted on a drive shaft 32 mounted in suitable bearings 325 and ll depending from the work table 11. lt will bc seen from this construction, that any rotation of the shaft l2 will be transmitted through the sprockets and chains to drive the work supporting spindles 16 and 1T in synchronism. 'lhc sha l't $32 may be driven by any suitable clutch controlled mechanism. This comprises a pulley rotatably mounted on a shalt il() which is supported in suitableV bearings 23T and 238 in the machine base. A sprocket 539 is mounted on the outer end ot the shal't 36 and is in turn connected by a link chain lll to a sprocket 41 which slidably keyed to the shaft 32. This sprocket l1 is provided with a key 42 so that the sprocket may he held against cndwise movement as the table l1 and shaft 32 reciprocate but at the same time permits rotation of theI shaft lil to drive the work spindles 16 and li'.

lt is desirable in a machine ot this type to provide some controll meclnuiisni for stopv ping and starting rotation ot the work .spindies. In the preferred construction, a clutch mechanism may be provided, such as a friction 'clutch of an old and well known type. This clutch comprises a cone-shaped member 43 which is slidably keyed to the shaftl 56 and is adapted to engage a correspondingly shaped aperture lll in the pulley 35. A coneshaped sleeve 45 is slidably. keyed on the shaft 3V and is adapted to engage the ends ot the long arm ot a plurality of clutch fingers 4h. The clutch lingers are pivotally mounted on a Supporting member l? and arranged so that the short arms i8 engage one face ot' the cone-shaped member 43. It will be read ilyapparcnt fromthisconstrnctiointliat when the sleeve is n'iovcd toward the right as viewed in Fig. 1. the lingers 4G are swung about their pivots and operate to slide the cone-shaped member lll into engagement with the aperture wall il to lock the pulley l5 to the shaft 36 and thereby start rotation of the spindles 16 and 17. -l yoked member if) engages an annular groove in the sleeve 45 so as to control the engaging or disengaging of the clutch. In order that the clutch sleeve 45 may be readily controlled, a manually operable lever 50 is pivotally mounted on the stud 51 so that the lever maybe swung in a vertical plane toward and from the machine base. The stud 51 is supported on a pivot 52 so that the lever may `be swung in a vertical plane substantiallyparallel with theways of the machine. The lever 50 is connected by a link 55 to the yoked member 49 which is pivotally mounted on a stud 56 so that any movement of the lever 50 longitudinally of the machine is transmitted to engage or disengagc the clutch. If the level' 50 is thrown toward the right, into a position as illustrated in dotted lines in Fig. 1, then the clutch operating sleeve 45 is moved toward the right to engage the clutch member and lock the pulley '35 to the shaft 36, thereby transmitting power to the spindles 16 and 17. If the operator moves the lever toward theleft, into the position as indicated in Fin. 1, then the sleeve 45 is moved toward the. le t and into engagement with a cone-shaped aperture wall 58 which is fixed on the machine base. The conesha jed sleeve is slidably keyed on the shaft 36 so that when it comes into engagement with the cone-shaped aperture wall 58, it will serve as a brake to stop the rotation of the work supporting spindles.

semi-automatic clamping mechanism is utilized, which will rigidly lock the shaft in place during grinding. As illustrated, the inner ends 'of the spindles 16 andlare provided with enlarged face plate portions 60 and 61 to which the work supporting and clamping heads 62 and 68 are securedrby means of bolts 64. Each of the heads 62 and 63 is provided with a. fixed partial bearing member 65 adapted to support one of the main bearings (i6-of a crankshaft 67. The surface of the bearing member 65 is arranged to support and align the shaft for grinding. A lever 68 is pivotally mounted on a stud 69 on the work heads 62 and 63 and is provided at its outer end with a projectin stud 70 which is threaded within the end o the lever 68 to permit adjustmentA of the stud relative to the lever. Itis readily apparent from this constructionfthat when the lever 68 is rocked about its pivot 69, the stud 70 is swung into engagement with thel periphery of the work and the shaft is held rigidly in position on the bearing member 65.

In the preferred construction, a toggle is provided to swing the lever 68 and to lock the crankshaft in rigid engagement with the work support-ing and rotating head. This may comprise a bell crank lever 72 which is provided with anfaperture 73 at its upper end adapted to loosely engage a spherically shaped projection 74 on the lever 68. The lower end of the lever 72 is pivotally mountlevers 106 ed on a stud 7 8 secured on the link 7 9 which is in turn pivoted on a stud in the work head member 62. It will be readily apparent from this construction, as illustrated in Fig. 2, that as the lever 72 is moved in the direction of the arrow, the pivot 80 being fixed, it will tend to raise the spherical projection 74 on the end of the lever 68 and swing the lever 68 about its pivot 69 to bring the stud 70 into engagement with the bearing 66 on the crankshaft 67 to hold the shaft rigidly in contact with the bearing member 65.

The toggle is preferably operated by a spring actuated mechanism to permit rotation of the work without disturbing the connections of the adjustment or operation of the clamping mechanism. As illustrated, rods and 86 are provided which pass through central apertures in the spindles 16 and 17 lrespectively. The inner end of each rod 85 and 86 is provided with a projecting portion 87 supporting a stud 88 which in turn supports the member 89. The member 89 is pivotally connected by a yoked member 90 to the short arm 91 of the bell crank lever 72 by stud 92. A screw threaded connection 95 is provided between the yoked member 90 and the member 89 so that the operator may readily adjust the position of the stud 92 relative to the operating mechanism. The rods 85 and 86 are each provided with an enlarged portion 96 which is adapted to act as a thrust receiving member for one end of spring 97 interposed between the enlarged portions 96 on the rods 85 and 86'and shoulder 98 in the aperture in spindles 16 and 17 respectively'. The portion 96 of the shafts 85 and 86 are slidably keyed to the aperture in the spindles 16 and 17 so that the shafts rotate with the spindles but are permitted to slide longitudinally thereof to operate the work clamping mechanism. It will be readily seen from this construction that the spring 97, which is of sullicient tension to exert the desired pressure to hold the crankshaft in the work supporting head, will exert a pressure on the spindle toward the work supporting head and thereby multaneously lock the end of the crankshaft in rigid engagement with the supporting member.

operate the toggle and si- In order that the crankshaft may be read- Y connected to the lower yoked ends 104 and 105 of levers 106 and 107 respectively. The and 107 are pivotally mounted on the studs 108 and 109 which are in fixed relation with the work supporting heads. The upper ends of these levers are formed yoked projections 110 and 111 which straddle and are connected to the members 112 and 118. The members 112 and 113 are in turn rotatably' supported by ball thrust bearings 114 on the outer end of the rods 85 and 8G to permit the spindles 1G and 17 and rods 85 and 86 to rotate and at the same time be given an endwise movement to lock and unlock the work supporting members.

A, suitable f'alve 115 is provided to control the tlow of tluid under pressure to actuate the piston. Fluid under pressure may be admitted to the valve 115 from any suitable well known fluid pressure source through the pipe 116 which enters the valve chamber 117 between the pistons 118 and 119 on the valve stem 120. This valve is of the balanced piston type arranged so that Huid entering the chamber 117 equalizes the pressure on each piston and permits a ready adjustment of the valve without undue exertion tn the part ot' the operator. lVhen the valve stem is moved outwardly so that the pistons 118 and 119 assume the dotted positions 122 and 128 respectively. the port is opened and fluid under pressure is permitted to pass through pipes 126 and 127 into the cylinder chambers 128 and 129 thereby moving the pistons 102 and 103 toward each other to swing the levers 106 and 107 and move the rods 85 and 8G outwardly against the tension of the .springs 97 to operate the toggles and thereby unlock the work clamps to release the crankshaft after the grinding operation has been completed.

It is. desirable that the work clamping mechanism and the clutch controlling the work rotation be so connected or inter-locked that the rotation of the work head cannot be started until the crankshaft is rigidly held in operating position. Likewise. when grinding has been completed, the rotation of the work heads should be stopped before the clamping members may be unlocked. To accomplish this. a lever controlling member 130 is provided for the lever 50. This member 130 is fixed to the base of the machine and is provided with a substantially L-shaped opening 181V which permits the lever 50 to be swung in a plane parallel with the work supporting spindles and also in a plane at right angles to said spindles. The valve stem 120 is connected to the lever 50 by means of a block which is lixed to the stem 125 and is slidably mounted in a T-shaped slot 130 in the lever 50 thereby permittingT a longitudinal swinging of the lever as well as a movement axially ot the valve stem 125.

Then the lever 50 is in the position illustrated in full lines in Figs. 1 and 4. the clutch 45 is disengaged. the spindles are stationary and the clamping mechanism unlocked.

Vhen the crankshaft is inserted in position on the partial bearing member 65, the operator moves the lever 50 into a position 50a., as shown in broken lines in Fig. l, to move the valve stem 120 and pistons 118 and 110 into a position shown in the dotted lines as 122 and 128. This movement closes the ports 125 and prevents furthe admission ot' lluid into the cylinder chamber. lVhen the` piston 11S) passes by and cuts ott' the port 125, the released tension ot' the springs 97 operating against the fluid in the cylinders, forces the fluid trom the cylinder chambers 128 and 129 and exhausts it through pipes 126 and 127, port 125 and pipe 1238. As the tension of the springs 07 is released, by the exhaust of the fluid, the rods and 86 are moved inwardly to operate the toggles and thereby swing the clamping lever (38 so that the studs 70 lock the crankshaft securely in position. The operator may then swing the lever 50 from position 50a. toward the right into position 507), as viewed in Figs. 1 and 4. This movement of lever 50 slides the clutch sleeve toward the right to lock the pulley $15 to the shaft 3G and thereby start rotation of thel spindles 1G and 17.

Similarly after the grinding operation is completed, the operator moves the lever 50 trom the position 507), as illustrated in bro` ken lines in Figs. 1 and al. into position 50u thereby moving the sleeve -15towards the left to contact with an aperture wall t ,i brake and stop the rotation of the spindles 16 and 17. After the rotation of the spindles has been stopped, the operator may swing the lever 50 from the position 50a (Fig. 4) into position 507 as shown in full lines, to move the Vvalve stem 20 and valve pistons from the dotted position 122and 123 into the position as shown in full lines 118 and 110. This permits luid under pressure to pass through the pipe 11G into the valve chamber 117 and through the ports 125 and pipes 120 and 127 into the cylinder chambers 128 and 120 ol the cylinders 100 and 101 respectively. The fluid under pressure in chambers 128 and 1211 moves the pistons 102 and 103 towards each other which operates to move the rods 85 and 86 away from' each other against the tension of the springs 97 to operate the toggle and unlock the crankshaft after grinding.

lt is desirable that the clamping members be unlocked only when (he hearing members G5 ot the work heads (i2 and 63 are in an upright position. To prevent the unlocking ot the clamping member 70 when the beau ings are in an inverted position` a safety device is provided including the yoke-shaped members and 141 which are secured to the heads 14 and 15 and straddle the rods 85 and 86 respectively. The rods 85 and 80 are provided with a spring pressed projection 142 which projects from the periphery of the shaft. This projection is on the same side of the shaft as the bearings 65 so that when the rods 85 and 86 are in the position as shown in Fig. 5, the shaft may be moved endwise to lock or unlock the clamping members. If the rods 85 and 86 stop so that the projection 142 is above the horizontal line passing through the axis' of the shaft, the projection 142 engages the side of the yoked members 140 and 141 to prevent end.--

wise movement of the rods 85 and 86, and thereby prevent locking or unlocking v.of the clamping members when the bearings 65 are in an inverted position.

If desirable, the spring actuated mechanism for operating the toggle of the clamping mechanism may be supplemented by a fluid pressure device so that the clamping pressure may be materially increased. This may be accomplished, as illustrated in Fig. 8, by admitting fluid under pressure to the pistons 102 and 103 so that they will be moved outwardly to exert a pressure on the lower end of the levers 106 and 107 which will move the rods 85 and 86 inwardlyl to increase the pressure exerted by the spring 97 on the toggle which operates the clamping jaw. As illustrated in the drawings,

a pipe 145 is connected to the cylinder to form a port 146 in the valve 115. This pipe is connected by ports 147 and 148 to the cylinder chambers 149 and 150 in the cylinders 100 and 101 respectively. An exhaust pipe 151 is connected to the valve casing 115 so that fluid may be exhausted from the system. When the valve stem 120 is moved to position the valve pistons as indicated in dotted lines, Fig. 8, at 122 and 123, the fluid under pressure passing through pipe 116, valve chamber 117, is forced through port 146, pipe 145 and ports 147 and 148 into the cylinder chambers 149 and 150 to move the pistons 102 and 103 outwardly and thereby increase the pressure on the toggle joints which clamp the work in place. When the valve stem 120 is moved to position the valve pistons 118 and 119 into the position as shown in full lines, Figs. 4 and 8, then the port 146 is cut off from the source of Huid pressure and the pistons 102 and 103 are forced towards each other to open the clamping jaws by the fluid pressure entering the chambers 128 and 129. This movementoperates to force the fluid from the` cylinder chambers 149 and 150 through ports 147 and 148 and through pipe 145, the port 146 and exhaust the fluid through the pipe 151. This Huid pressure may be used to supplement` the pressure of the spring actuated mechanism if additional4 pressure on the work clamping members is desirable.

The operation of this mechanism will be readily apparent from the foregoing disclosure. The operator places the crankshaft 67 in positionon'the bearings 65, then moves the lever 50 from the position shown in full lines (Figs. 1 and 4 which, as previously permit Huid to exhaust from the cylinders and the tension of the spring 97 to cause an axial movement of the rods 85 and `86 which in turn operate to lock the shaft rigidly in operating position on the heads 62 and 63. The operator then swings the lever 50 from the position 50a into position 505, as shown in Figs. 1 an-d 4, which starts rotation of the Work. The operator then turns the wheel feeding mechanism (not shown) to feed the grinding wheel into the Work to reduce the -crankpin to the desired size. After the pin has been finish ground, the operator removes the grinding wheel from operative engagement with the work and then stops the work rotation by moving the lever 50 from the position 50?) into position 50a and may then throw the lever 50 into the position shown in full lines in Fig. 4to unclamp the work after the grinding has been completed.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is: f

1. A work supporting and rotating mechanism for a grinding machine comprising a rotatable spindle, a work supporting and clamping device mounted on said spindle, means including a clutch to rotate said spindle, means including a Huid pressure device arranged to operate said clamping device, and a manually operable lever arranged to operate said clutch when moved in one direction and to control said fluid pressure device when moved in another direction.

2. work supporting and rotating mechanism for crankshaft grinding machines comprising a rotatable spindle, means including a clutch to rotate said spindle, means including a clamping jaw movably mounted on the spindle to support the work during rotation thereof, a spring actuated mechanism to move said jaw to clamp the work rigidly in place, means including a fluid pressure device arranged to operate said jaw against the tension of said mechanism to permit removal of the work piece after grinding, and a manually operable lever connected to operate said clutch when moved in one direction and to control said fiuid pressure device when moved in another direction.

to a position 50a' escribed operates to 8. A work supporting and rotating mechy anism for grinding machines comprising a v ed to the valve device and to the clutch to control the stopping and starting of the work rotationand the admission of fluid into said device to lock and unlock the work.

4. A work supporting and rotating mechanism for a grinding machine comprising a rotatable spindle, means including a clutch to rotate the spindle, a work supporting member including a clamping jaw and an opposed work bearing member rotatable with the spindle to support a work piece thereon, a fluid pressure actuated device to operate said jaw, manual means to control the clutch and to control said device and clamping jaw, and means associated therewith necessitating movement of the clamping jaw to engage the Work before the clutch can be thrown to rotate the spindle.

5. A work supporting and rotating mechanism for a grinding machine comprising a rotatable spindle, means including a clutch to rotate the spindle, means including a clam ing jaw and an opposed work bearing member which is rotatable with the spindle to support a work piece thereon, a fluid pressure actuated device to operate said jaw, manual means to control the clutch and to control said device and clamping member, and means associated therewith to prevent the clamping member from being disengaged before the clutch has been thrown to stop the work rotation.

6. A work supporting and rotating mechanism for grinding machines comprising a spindle, a work supporting member mounted on said spindle, a clamping jaw arranged to engage the work piece, a toggle arranged to operate said j aw, and a spring actuated mechanism operatively connected to actuate said ltOoggle to rigidly lock the work in said mem- 7 A work supporting and rotating mechanism for rinding machines comprisin a rotatable spindle, a work supporting mem r xedly mounted on said spindle, a clamping jaw on the supporting member arranged to engage the work piece, a toggle arranged to actuate said jaw, a spring actuated mechanism operatively connected to said toggle to simultaneously operate said jaw to rigidly clamp the work on said member, and a fluid pressure mechanism connected to the toggle to move the clamping jaw to release the work.

8. A grinding machine comprising a slidably mounted table, means including a rotatable spindle on said table for supporting a work piece, a movable clamping jaw revolving with the spindle and cooperating therewith to hold the work piece in place, a Huid pressure device ixedly mounted on said table and connections between said device and the revolving jaw to actuate said clamping jaw.

9. A grinding machine comprising a slidably mounted table, a pair of rotatable spindles on said table, work supporting members fixedly mounted on said spindles and arranged to revolve therewith and to support opposite ends of the work, a clamping jaw cooperating with each member and revolving with the spindle to hold the work piece in place, a spring actuated mechanism vconnected to move the clamping jaws to grip the work, a fluid pressure mechanism rigidly mounted on said table and a connecting device between the jaw and said fluid pressure mechanism to oppose the spring actuated mechanism and unlock the jaw to permit removal of the work piece after grinding.

l0. A work supporting and rotating mechanism for a grinding machine comprisin a rotatable spindle, a work supporting mem er mounted on said spindle, a clamping 'aw on said member arranged to lock the wor piece rigidly in place, a toggle on said member arranged to operate sa1d jaw, a rod assing through a central aperture in said splndle to operate the toggle and the jaw, and mechanism connected to move said rod.

11. A work supporting and rotating mechanism for a grinding machine comprising a rotatable holder and a movable jaw arranged to clamp against the peripheral portion of an end of the work, means to operate the jaw, and means to prevent operation of the jaw when the holder isin an inverted from which the work could `fall w en released.

12. A work supporting and rotating mechanism for a grinding machine comprising a rotatable spindle, a Work supporting member fixedly mounted on said spindle, a clamping jaw arranged to engage the work piece, means including a fluid pressure device arranged to operate said jaw, and means to preventunlocking of said jaw when said member is in an inverted position.

13. A work supporting and rotating mechanism for a grinding machine comprising a rotatable spindle, work supporting members fixedly mounted on said spindle, a clamping jaw arranged to engage the work piece, a spring actuated mechanism to lock said jaw to clamp the work rigidly on said member, manually controlled mechanism to unlock said j aw to permit removal of the work piece after grinding, and means to prevent unlocking of said jaw when said member is in an inverted position.

14. A work supporting and rotating mechanism for a grinding machine comprising a rotatable spindle, a work supporting member fixedly mounted on said spindle, a clamping jaw arranged to engage the work piece, a spring actuated mechanism to lock said jaw to clamp the work rigidly on said member, means including a fiuid pressure device arranged to operate said jaw, and means to prevent unlocking said jaw when said member is in an inverted position.

osition 15. A work supporting and rotating mechanism for a grinding machine comprising a. rotatable hollow spindle, a work supporting member on said spindle, a clamplng jaw opposed to said member and arranged to look the Work piece rigidly in place, a rod passing through said spindle, connections between said jaw and rod to aetuate said jaw, and a. fluid pressure mechanism connected to move said rod.

Signed at Worcester, Massachusetts, this 2nd day of November, 1928.

HERBERT A. SILVER.v ALBERT G. BELDEN. 

